A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus are conventionally used, for example, in the manufacture of integrated circuits (ICs), flat panel displays and other devices involving fine structures.
It is desirable to reduce the size of features in a lithographic pattern because this allows for a greater density of features on a given substrate area. In photolithography, the increased resolution may be achieved by using radiation of shorter wavelength. However, there are problems associated with such reductions. Current systems are starting to, adopt optical sources with wavelengths in the 193 nm regime but even at this level, diffraction limitations become a barrier. Optical lithography machines capable of enhanced resolutions typically require complex optics, rare materials, and/or cumbersome techniques and are consequently rather expensive.
An alternative for printing small features comprises transferring a pattern to a substrate by imprinting a pattern into an imprintable medium using a physical mould or template, and is also known as imprint lithography. The imprintable medium may be the substrate or a material coated onto a surface of the substrate. The imprintable medium may be functional or may be used as a “mask” to transfer a pattern to an underlying surface. The imprintable medium may for instance be provided as a resist deposited on a substrate such as a semiconductor material to which the pattern defined by the template is to be transferred. In imprint lithography the topography of a template thus largely defines the patterns created on a substrate.
In so-called UV imprint lithography, the imprintable medium may be cured by irradiating the medium with radiation that has passed through the template. Due to its transparency to radiation, and also because of its hardness, the template in UV imprint is often made of quartz. A disadvantage of quartz templates, however, is their cumbersome manufacture and replication.